The present invention relates to arrowheads attachable to the end of a shaft and including a blade mounting assembly which allows retraction and extension of the blades relative to the outer perimeter of the arrowhead. More particularly, the present invention relates to arrowheads attachable to a shaft and including outwardly movable blades arranged for minimum extension during flight and maximum extension upon impact at a target. A significant utility for the present invention is in hunting of large game animals with arrows in a manner which maximizes the probability of killing of the target animal but is humanely adapted for permitting the animal to withdraw the arrow in the event that a kill is not effected.
Conflicting requirements are placed upon the arrows to be used by an archer when hunting game animals, fish and the like. While in flight, the diameter of the arrowhead should be minimal to increase flight stability especially when used in a bow with heavy draw weight. However, it is extremely difficult to bring down a large animal with an arrowhead having such a small diameter. Some broad heads using fixed, outwardly extending blades of a larger diameter have been developed to increase the cutting size upon impact but the extended blades significantly decrease the in-flight stability. That is, such broad heads tend to plane or wobble and are especially sensitive to wind thereby significantly discounting accuracy of the archer as the distance from the target increases. Accordingly, there have been several arrowheads developed for the intended purpose of retaining the blades in a retracted position during flight but expanding those blades into a larger cutting diameter at or after impact on the target.
Several of the prior art developments have been directed towards arrangements wherein blades are pivotally mounted and adapted for forward extension relative to the arrow shaft during flight but pivoted into an outwardly extended position upon impact. Examples of such devices are in U.S. Pat. Nos. 2,568,417 by Steinbacher, 2,820,634 by Vance, 2,993,697 by Urban and 3,578,328 by Rickey. Such devices as those shown by Steinbacher, Vance and Rickey include extensions on the blade which engage the target and expand into the outwardly extended position after entry into the target. Urban employs a pivotal linkage arrangement for outwardly extending the cutting blades which are likewise pivotally attached at their points. Arrows impacting a game animal do not always kill that animal which sometimes escapes. In fact, it has been suggested that less than twenty percent of the game animals hit by arrows are actually captured by the hunter. Accordingly, for humane and conservation reasons, it is imperative and even a legal requirement in some jurisdictions that arrowheads be removable by the animal so as to reduce further internal injury and infection and allow natural healing to prevent waste of that animal. Although some of the prior art devices accommodate withdrawal of the arrow by the animal, the arrowheads frequently do not produce a large external wound but only expand after entry into the target which means that the animal may eventually die from internal hemorrhaging but will not leave a blood trail to permit the hunter to retrieve the carcass. Therefore, it is not only imperative that the cutting blades of the arrowhead be expandible upon impact from an in-flight retracted position but that this expansion be effected immediately upon impact so as to produce a large external wound.
Other prior art arrowhead developments have been directed towards mechanisms for retaining the cutting blades in a backwardly folded retracted position during flight with outward expansion upon or after impact with the target. Examples of such devices are shown in U.S. Pat. Nos. 2,859,970 by Doonan, 3,014,305 by Yurchich, 3,036,396 by Swails and 3,738,657 by Cox. Unfortunately, the backward folded blade configurations of the prior art do not meet the requirements of permitting retraction of the arrowhead by the animal at least not without creating substantial additional internal injury to the animal since the blades are retained against any forward pivoting thereof. Still further, such backwardly folded blade arrowhead configurations frequently involve relatively complex internal mechanisms and thus are not well suited for component replacement in the field. Although Doonan shows internal camming cones for forcing the blades into the outwardly extended position, these blades cannot be forwardly pivoted to allow extraction by the animal and further the camming mechanism and blade mounting is relatively weak because of the internal camming apparatus and the arrangement for blade mounting therein. Furthermore, an arrowhead of the Doonan type using an internal camming plunger can only employ two blades mounted in a common pin. However, it has been found in practice that preferably at least three blades should be included to improve flight stability while increasing the effective cutting area on impact.
Accordingly, there has been a continuing need in the prior art for an arrowhead which retains the cutting blades in minimal outwardly extended position during flight but which can be outwardly expanded upon impact to create a maximum external cutting at the target while accommodating forward pivotal movement of the blades as for extraction by an animal. Still further, there has been a continuing demand for such an arrowhead assembly using expandible/retractible blades with relatively simple but easily replaced components in the field. The need for such an arrowhead which is of minimal weight but fabricated from reliably operable elements for long term usage likewise exists. Still further, there has been a continuing need for an expandible arrowhead which permits field selection of the amount of outward blade pivoting upon impact.